Imperial Standard Wire Gauge
Imperial Standard Wire Gauge , introduced as Standard Wire Gauge , abbreviated SWG , further development of the Birmingham Wire Gauge (BWG) , is a British coding for solid wire and is specified in the outdated BS 3737: 1964 standard.
The growing supra-regional and international trade in wires and cables forced Britain at the end of the 19th century to standardize the approximately 40 different gauge systems for solid wire that had been in use up to that point. Until then, bad purchases were the order of the day due to different gauge coding systems and different coding tables. Especially after the continental competitors France and Germany had agreed on dimensions for wires according to the metric system, a uniform coding table became urgent.
The British Board of Trade looked for a solution in coordination with manufacturers and umbrella organizations.
First of all, the widely used Birmingham Wire Gauge (BWG) was examined for its suitability by the "Warden of the Standard". The BWG is an empirically developed gauge system, the origin of which is too far in the past to be determined. It was speculated that the gauge numbers from 1 upwards were originally based on a reduction in cross-sectional area of 20 percent. According to the assumption at the time, the wire cross-sections were later changed for reasons of practicality during manufacture or because of the requirements of the markets. It was also recognized that there was no reference list for the BWG, as it is nowadays, but manufacturers and retailers had adapted the lists to their needs and thus more or less different wire diameters were traded under the same BWG gauge number. As early as 1877 it was therefore clear that the BWG could not become a standard.
In 1879, a committee of the British Society of Telegraph Engineers set out to select a gauge system as the standard system. The task was difficult because in no area had a single gauge system prevailed. At the end of the process, the committee suggested the relatively uncommon Latimer Clark's Wire Gauge, which hadn't been developed until 1867. It is based on a constant percentage change in diameter, like the American Wire Gauge (AWG), but the graduation and the diameter were chosen so that the gauge numbers roughly corresponded to those of the BWG.
After consultation with manufacturers and the Board of Trade, the Order of Council introduced a significantly improved Birmingham Wire Gauge on August 23, 1883 under the name "Standard Wire Gauge" and had been the official unit of measurement for wire diameters in the United Kingdom since March 1, 1884.
This new measuring system for wires only coincided with the diameter of 1 gauge BWG for 1 gauge SWG. At the next gauge number, the wire cross-section changed in steps of about 20%. Deviations from this percentage are due to the drawing steps during manufacture. The basis of the SWG is the length dimension mil , which corresponds to 0.001 " . The smallest diameters have even been defined with an accuracy of 0.0001".
At the time of its inception, the United States did not yet have a government-established gauge system for wires. The new British Standard Wire Gauge was discussed there, but ultimately Congress in March 1893 did not prescribe a gauge system for metal wire. Over time, the American Wire Gauge for non-ferrous metal wires, e.g. B. for electrical wiring, and the US Steel Wire Gauge (Washburn & Moen Gauge) for steel wires.
SWG was replaced in 1986 by the standard BS 6722: 1986 based on metric measurements.
The largest wire number with the designation 7/0 Gauge SWG has a diameter of 0.5 "(12.7 mm), the smallest wire diameter with the designation 50 has a diameter of 1 mil (25.4 µm). The weight reduction per unit length between two adjacent wire diameters is approximately 20%, the ratio of two adjacent diameters v is reduced approximately by 10.6% per step according to the following equation:
The table of the specific wire diameters in the SWG system is:
| Standard wire gauge designation |
inch | mm | Increment |
|---|---|---|---|
| 7/0 | 0.500 | 12,700 | 0.036 "/ gauge |
| 6/0 | 0.464 | 11.786 | 0.032 ″ / gauge |
| 5/0 | 0.432 | 10.973 | |
| 4/0 | 0.400 | 10.160 | 0.028 "/ gauge |
| 3/0 | 0.372 | 9.449 | 0.024 ″ / gauge |
| 2/0 | 0.348 | 8,839 | |
| 0 | 0.324 | 8.230 | |
| 1 | 0.300 | 7.620 | |
| 2 | 0.276 | 7.010 | |
| 3 | 0.252 | 6.401 | 0.020 ″ / gauge |
| 4th | 0.232 | 5,893 | |
| 5 | 0.212 | 5.385 | |
| 6th | 0.192 | 4,877 | 0.016 ″ / gauge |
| 7th | 0.176 | 4,470 | |
| 8th | 0.160 | 4.064 | |
| 9 | 0.144 | 3.658 | |
| 10 | 0.128 | 3.251 | 0.012 "/ gauge |
| 11 | 0.116 | 2.946 | |
| 12 | 0.104 | 2,642 | |
| 13 | 0.092 | 2,337 | |
| 14th | 0.080 | 2.032 | 0.008 ″ / gauge |
| 15th | 0.072 | 1,829 | |
| 16 | 0.064 | 1.626 | |
| 17th | 0.056 | 1.422 | |
| 18th | 0.048 | 1.219 | |
| 19th | 0.040 | 1.016 | 0.004 ″ / gauge |
| 20th | 0.036 | 0.914 | |
| 21st | 0.032 | 0.813 | |
| 22nd | 0.028 | 0.711 | |
| 23 | 0.024 | 0.610 | 0.002 ″ / gauge |
| 24 | 0.022 | 0.559 | |
| 25th | 0.020 | 0.5080 | |
| 26th | 0.018 | 0.4572 | 0.0016 ″ / gauge |
| 27 | 0.0164 | 0.4166 | |
| 28 | 0.0148 | 0.3759 | 0.0012 ″ / gauge |
| 29 | 0.0136 | 0.3454 | |
| 30th | 0.0124 | 0.3150 | 0.0008 ″ / gauge |
| 31 | 0.0116 | 0.2946 | |
| 32 | 0.0108 | 0.2743 | |
| 33 | 0.0100 | 0.2540 | |
| 34 | 0.0092 | 0.2337 | |
| 35 | 0.0084 | 0.2134 | |
| 36 | 0.0076 | 0.1930 | |
| 37 | 0.0068 | 0.1727 | |
| 38 | 0.0060 | 0.1524 | |
| 39 | 0.0052 | 0.1321 | 0.0004 ″ / gauge |
| 40 | 0.0048 | 0.1219 | |
| 41 | 0.0044 | 0.1118 | |
| 42 | 0.004 | 0.1016 | |
| 43 | 0.0036 | 0.0914 | |
| 44 | 0.0032 | 0.0813 | |
| 45 | 0.0028 | 0.0711 | |
| 46 | 0.0024 | 0.0610 | |
| 47 | 0.0020 | 0.0508 | |
| 48 | 0.0016 | 0.0406 | |
| 49 | 0.0012 | 0.0305 | 0.0002 ″ / gauge |
| 50 | 0.0010 | 0.0254 |